Products of HY-1C/D ocean color satellites and their typical applications

Abstract

The HY-1C and HY-1D satellites are the first operational ocean color constellation in China. HY-1C and HY-1D was launched in September 7, 2018 and Jun 11, 2020, respectively. Chinese Ocean Color and Temperature Scanner (COCTS), Coastal Zone Imager (CZI), Ultra-Violet Imager (UVI), Satellite-based Calibration Spectrometer (SCS) and Automatic Identification System (AIS) are the key payloads onboard HY-1C and HY-1D. The HY-1C/D constellation has been detecting the global ocean color twice and sea surface temperature (SST) four times every day, and high- resolution (50m) China’s coastal zone and offshore environments twice every three days. In this article, the HY-1C/D satellites and the specifications of the payloads, flow-process, product levels and distribution of data products are introduced. The overpass times are 10:30 am±30 min and 1:30 pm±30 min of local time at the descending node for HY-1C and ascending node for HY-1D, respectively. The HY-1C/D satellites complete processing chains for generating raw data, radiances, ocean color and Sea Surface Temperature (SST) from the payloads by Geo-location, radiometric and atmospheric correction, geophysical parameters retrieval, data gridding and merging. There are different data products associated with the five levels of processing (Level 0 to Level 4). Data products of Level-1 (radiances), 2 (ocean color parameters and SST), 3 (gridded products) and 4 (merged gridded products) are available from the China Ocean Satellite Data Service Center to the general public for free. The HY-1C/D satellites product structure system is complete and data product processing and distribution are efficient. The typical products of Chlorophyll-a concentration and SST, the applications on floating green tides algae Ulva prolifera, sea ice, offshore aquaculture, inland water and tropical cyclones are also presented in this article. Maps of global daily gridded chlorophyll-a concentration and SST (L3A products) from COCTS onboard the HY-1C and HY-1D are presented to show their temporal and spatial coverage. The CZI remote sensing images have being used to extract the distribution location and area of offshore green tide, sea ice and offshore aquaculture facilities. The process of ice shelf falling off and drifting around Antarctic continent has been monitored by using a long time series CZI remote sensing images. In addition to offshore and coastal environmental monitoring applications, HY-1C/D remote sensing data products have also been applied in inland water algal bloom, typhoon cloud map and its moving path monitoring. The typical products and application shown in this article indicates that the sensors and the data products of HY-1C/D have high quality and great application potential in marine and coastal environmental monitoring. The planned future satellites including the next generation of Chinese ocean color satellites and geostationary coastal zone and ocean environment monitoring satellite and their key specifications are briefly introduced. The new generation satellites with more spectral channels, broader spectrum range, and higher temporal and spatial resolution will have greater application potential in monitoring of ocean color and coastal zone ecology, resources and environment.